Wloga Dorota, Camba Amy, Rogowski Krzysztof, Manning Gerard, Jerka-Dziadosz Maria, Gaertig Jacek
Department of Cellular Biology, University of Georgia, Athens, GA 30602-2607, USA.
Mol Biol Cell. 2006 Jun;17(6):2799-810. doi: 10.1091/mbc.e05-05-0450. Epub 2006 Apr 12.
The genome of Tetrahymena thermophila contains 39 loci encoding NIMA-related kinases (NRKs), an extraordinarily large number for a unicellular organism. Evolutionary analyses grouped these sequences into several subfamilies, some of which have orthologues in animals, whereas others are protist specific. When overproduced, NRKs of three subfamilies caused rapid shortening of cilia. Ultrastructural studies revealed that each NRK triggered ciliary resorption by a distinct mechanism that involved preferential depolymerization of a subset of axonemal microtubules, at either the distal or proximal end. Overexpression of a kinase-inactive variant caused lengthening of cilia, indicating that constitutive NRK-mediated resorption regulates the length of cilia. Each NRK preferentially resorbed a distinct subset of cilia, depending on the location along the anteroposterior axis. We also show that normal Tetrahymena cells maintain unequal length cilia. We propose that ciliates used a large number of NRK paralogues to differentially regulate the length of specific subsets of cilia in the same cell.
嗜热四膜虫的基因组包含39个编码NIMA相关激酶（NRK）的基因座，对于单细胞生物来说这是一个非常庞大的数目。进化分析将这些序列分为几个亚家族，其中一些在动物中有直系同源物，而其他的则是原生生物特有的。当三个亚家族的NRK过量产生时，会导致纤毛迅速缩短。超微结构研究表明，每个NRK通过一种独特的机制触发纤毛吸收，该机制涉及轴丝微管的一个子集在远端或近端的优先解聚。激酶失活变体的过表达导致纤毛延长，表明组成型NRK介导的吸收调节纤毛的长度。每个NRK根据沿前后轴的位置优先吸收不同的纤毛子集。我们还表明，正常的嗜热四膜虫细胞保持不等长的纤毛。我们提出，纤毛虫使用大量的NRK旁系同源物来差异调节同一细胞中特定纤毛子集的长度。
